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UNIVERSITY  OF  ILLINOIS 

Agricultural  Experiment  Station 


BULLETIN  NO.  279 


THE  TOXICITY  OF  SALT 
FOR  CHICKENS 

By  H.  H.  MITCHELL,  L.  E.  CARD,  AND  G.  G.  CARMAN 


The  presence  of  small  amounts  of  salt  in  various  feeds  for 
poultry  is  not  so  dangerous  as  has  commonly  been  believed. 
This  bird  was  raised  on  a  ration  containing  8  percent  of  salt. 


URBANA,  ILLINOIS,  JULY,  1926 


SUMMARY 

Because  of  the  general  belief  that  chickens  are  very  readily  pois- 
oned by  common  table  salt,  and  because  of  the  common  occurrence  of 
salt  in  wastes  and  by-product  feeds  for  poultry,  it  was  considered  im- 
portant to  determine  definitely  whether  the  use  of  such  wastes  and 
feeds  is  dangerous  to  health  or  retards  growth.  This  experiment  was 
planned,  therefore,  in  order  to  determine  (1)  the  maximum  percentage 
of  salt  that  may  be  fed  to  growing  chickens  without  harmful  results, 
and  (2)  the  maximum  single  dose  of  salt  that  a  chicken  can  tolerate, 
or  the  smallest  dose  that  would  cause  death. 

In  all,  75  chickens  from  three  breeds  were  used.  Fifty  chickens 
were  given  a  basal  ration  made  up  of  yellow  corn,  bran,  dried  butter- 
milk, steamed  bone  meal,  and  ground  limestone,  containing  percent- 
ages of  salt  of  1,  2,  4,  and  8.  Twenty-five  other  chickens  were  used  in 
determining  the  maximum  single  dose  of  salt  that  an  adult  chicken 
can  tolerate. 

It  was  found  that  chickens  could  be  raised  from  9  to  21  weeks  of 
age  on  rations  containing  as  high  as  8  percent  of  salt  with  no  appar- 
ently detrimental  effects.  While  it  took  some  time  for  the  chickens  to 
become  accustomed  to  such  a  salty  ration,  they  soon  learned  to  eat  it 
in  amounts  sufficient  to  promote  a  rate  of  growth  approximately  the 
same  as  that  of  chickens  fed  the  check  ration. 

When  the  salt  was  mixed  in  the  feed,  a  daily  intake  of  6  to  8 
grams  of  salt  per  bird  appeared  to  have  no  harmful  effect  on  the  birds 
that  were  9  weeks  old  or  older. 

Salt  put  directly  into  the  crop  in  two  equal  doses  amounting  to  12 
to  16  grams  daily  was  quickly  fatal  in  the  case  of  birds  weighing  2  to 
4  pounds  each. 

Salt  given  in  solution  twice  daily  proved  to  be  more  toxic  than 
equal  amounts  consumed  in  the  feed. 

The  minimum  lethal  single  dose  of  salt  for  birds  weighing  from  3 
to  5  pounds  was  found  to  be  close  to  4  grams  per  kilogram  of  body 
weight. 


By  H.  H.  MITCHELL,  L.  E.  CARD,  AND  G.  G.  CARMAN' 

It  is  a  general  belief  among  poultrymen  that  chickens  are  very 
readily  poisoned  by  common  table  salt,  and  many  instances  have  been 
reported  in  which  chickens  were  killed  by  eating  salt  meat  or  fish, 
salty  kitchen  wastes,  or  brine  left  from  the  curing  of  meat  or  from  the 
freezing  of  ice  cream.  It  has  been  recommended  by  some  writers  that 
the  proportion  of  salt  in  a  mash  for  chickens  be  no  higher  than  5  to  10 
ounces  to  100  pounds  of  mash  when  the  mash  mixture  comprizes  about 
half  the  total  ration,  and  that  no  salt  be  given  to  young  stock  until 
they  are  two  months  old.  However,  only  a  few  controlled  experiments 
concerned  with  a  determination  of  the  minimum  lethal  dose  of  salt  for 
chickens  have  been  reported  in  the  literature. 

In  1892  Collier2  reported  the  results  of  feeding  varying  amounts  of 
salt  to  mature  hens.  No  harmful  results  were  noticed  in  these  experi- 
ments involving  six  hens  until  the  intake  of  salt  reached  0.063  ounce 
per  head  per  day.  An  intake  of  0.042  ounce  per  head  per  day  was  not 
accompanied  by  any  noticeable  symptoms.  In  1909  Suffran3  attempted 
to  determine  the  minimum  toxic  dose  of  common  salt  for  chickens. 
From  experiments  on  5  chickens,  he  concluded  that  a  dose  of  4  grams 
per  kilogram  of  body  weight  is  sufficient  to  produce  death,  tho  one 
chicken  in  the  experiment  resisted  this  dose  successfully.  Salt  was  ad- 
ministered in  solution  and  was  injected  into  the  crop  after  the  meal. 
The  symptoms  noticed  were  inability  to  stand,  intense  thirst,  pro- 
nounced muscular  weakness,  and  convulsive  movements  just  before 
death.  A  viscous  discharge  from  the  beak  was  also  noted.  Post- 
mortem examination  revealed  lesions  in  many  organs,  but  particularly 
hemorrhages  and  a  severe  congestion  in  the  gastro-intestinal  tract. 

The  attention  of  Edwards4  was  directed  toward  the  problem  by 
a  case  in  which  several  ducks,  pigs,  and  chickens  were  killed  by  being 
fed  the  sweepings  from  the  floor  of  a  bakery,  afterward  found  to  con- 
tain about  22  percent  of  salt.  The  symptoms  noted  in  the  chickens 
were  very  similar  to  those  above  reported.  An  experiment  was  then 

1H.  H.  Mitchell,  Chief  in  Animal  Nutrition;  L.  E.  Card,  Chief  in  Poultry 
Husbandry;  G.  G.  Carman,  formerly  Assistant  in  Animal  Nutrition. 

'Collier,  Peter.    N.  Y.  Agr.  Exp.  Sta.  (Geneva),  Bui.  39,  N.  S.    1892. 

'Suffran,  F.  Rev.  Gen.  Med.  Vet.  13,  No.  156,  698-705.  1909.  Exp.  Sta. 
Rec.  23,  793.  1910. 

'Edwards,  J.  T.    Jour.  Compar.  Path,  and  Ther.  31,  40-43.     1918. 

135 


136  BULLETIN  No.  279  [.July, 

performed  upon  three  pigeons.  Solutions  containing  0.625,  1.25,  and 
2.50  grams  of  salt  per  kilogram  of  body  weight,  respectively,  were  in- 
jected into  the  crops  of  the  birds.  No  ill  effects  from  these  doses  were 
noted,  except  a  temporary  depression  of  the  two  birds  given  the  largest 
doses.  Five  days  later  the  same  birds  received  doses  amounting  to 
2.50,  3.33,  and  4.50  grams  per  kilogram  of  body  weight.  The  bird  re- 
ceiving the  highest  dose  died  in  18  hours,  the  bird  receiving  the  next 
highest  dose  died  in  23  hours,  while  the  one  receiving  the  smallest  dose 
showed  no  symptoms. 

Other  experiments  concerned  with  the  symptoms  of  salt  poisoning 
have  been  performed,1  but  in  these  experiments  no  attempt  was  made 
to  determine  the  smallest  toxic  dose  of  salt.  They  need  not,  therefore, 
be  reviewed  here. 

The  evidence  bearing  on  the  toxicity  of  salt  for  chickens  is  meager 
and  somewhat  contradictory.  Because  of  the  common  occurrence  of 
salt  in  domestic  and  industrial  wastes  and  by-product  feeds  that  are 
occasionally  or  regularly  fed  to  poultry,  it  is  of  importance  to  deter- 
mine definitely  whether  the  use  of  these  wastes  and  feeds  is  a  constant 
source  of  danger  to  the  poultry  flock.  The  experiments  reported  in 
this  bulletin  were  undertaken,  therefore,  with  two  objects  in  view: 
first,  to  determine  the  effect  of  varying  percentages  of  salt  in  the  ration 
on  the  rate  of  growth  of  chickens;  and  second,  to  determine  the  small- 
est dose  that  would  cause  death. 

OUTLINE  OF  EXPERIMENT 

Five  lots  of  10  chicks  each  at  the  poultry  farm  and  five  lots  of  5 
chicks  each  at  the  nutrition  laboratory  were  fed  a  well-balanced  basal 
ration  containing  varying  amounts  of  salt.  Lot  1  at  both  the  poultry 
plant  and  the  nutrition  laboratory  received  1  percent  of  salt  in  their 
ration;  Lot  2,  2  percent;  Lot  3,  4  percent;  Lot  4,  8  percent;  and  Lot 
5,  1  percent  with  free  access  to  rock  salt.  The  lots  fed  at  the  poultry 
farm  were  kept  in  shelters  open  to  the  south  and  had  the  run  of  lots 
free  from  vegetation  (Fig.  1).  They  were  group-fed  and  were  weighed 
individually  each  week.  Feed  records  were  kept  on  all  lots. 

The  chickens  grown  in  the  laboratory  were  confined  in  individual 
pens  having  a  floor  space  of  4  square  feet.  They  were  fed  individu- 
ally and  were  weighed  weekly. 

All  lots  had  free  access  to  feed  at  all  times,  and  the  chickens  fed 
individually  at  the  nutrition  laboratory  were  also  given  as  much  feed 
as  they  would  consume.  It  was  hoped  that  all  chickens  in  the  experi- 
ment could  be  selected  from  the  same  breed  of  birds  at  the  same  age, 
but  unfortunately  this  ideal  could  not  be  realized.  Each  lot  kept  at 


'Heinz  and  Haas.    Munchen.    Med.  Wchnschr.  70,  565-66.     1923. 


1926] 


THE  TOXICITY  OF  SALT  FOR  CHICKENS 


137 


the  poultry  farm  contained  5  White  Wyandotte  chickens  and  5  White 
Leghorn  chickens.  The  chickens  grown  at  the  nutrition  laboratory 
were  all  Rhode  Island  Reds.  The  initial  age  of  all  chickens  was  8 
weeks.  In  the  distribution  of  the  birds  among  the  several  lots,  the 
number  of  cockerels  and  pullets  in  each  lot  was  made  the  same. 


FIG.  1. — EXPERIMENTAL  FEEDING  PENS  AT  THE  POULTRY  PLANT  USED 

FOR  THE  VARIOUS  LOTS 

Chicks  fed  at  the  poultry  farm  were  Jtept  in  shelters  open  to  the 
south  and  had  the  run  of  the  lots,  which  were  free  from  vegetation. 


The  feeding  experiment  at  the  poultry  farm  was  continued  for  13 
weeks  and  that  at  the  nutrition  laboratory  for  12  weeks.  At  the  end 
of  this  time  the  birds  were  given  salt  either  in  capsules  or  in  solution, 
in  order  to  determine  the  minimum  amount  they  could  tolerate  in  re- 
peated doses  and  the  minimum  single  toxic  dose. 


EXPERIMENTAL  RESULTS 

The  rations  used  at  the  poultry  farm  and  at  the  nutrition  labora- 
tory are  given  in  Table  1.  The  lots  at  the  farm  and  at  the  laboratory 
receiving  equal  percentages  of  salt  will  be  referred  to  by  the  same 
numbers.  Lot  5  differed  from  Lot  1  in  having  access  to  salt  at  all 
times  besides  receiving  1  percent  in  its  feed.  It  was  found,  however, 
that  these  chickens  did  not  consume  any  of  the  salt  offered  to  them,  or 
if  any  was  consumed  it  was  so  small  an  amount  as  to  be  obscured  by 
the  changes  in  moisture  content  of  the  salt  offered.  The  salt  intake 
of  Lots  1  and  5  was  therefore  the  same. 


138 


BULLETIN  No.  279 


[.July, 


For  the  first  week  of  the  experiment  all  lots  were  fed  the  ration 
containing  1  percent  salt.  On  June  26,  1925,  the  lots  were  put  upon  the 

TABLE  1. — BASAL  RATION  AND  VARIATIONS  IN  SALT  CONTENT  FOR  VARIOUS 

LOTS  OF  CHICKENS 


Feed 

Lots 
1  and  5 

Lot  2 

Lot3 

Lot  4 

Corn  

60 

59 

57 

53 

Wheat  bran  

15 

15 

15 

15 

Dried  buttermilk  

15 

15 

15 

15 

Steamed  bone  meal  

5 

5 

5 

5 

Calcium  carbonate  (CaCOs)  

4 

4 

4 

4 

Common  salt  (NaCl)  

1 

2 

4 

8 

Ninety-eight  parts  of  the  above  mixture  was  in  each  case  mixed  with  2  parts  of 
cod-liver  oil. 

different  experimental  rations  and  kept  under  observation  for  12  weeks 
in  the  case  of  the  birds  at  the  poultry  plant,  and  for  11  weeks  in  the 
case  of  the  birds  in  the  nutrition  laboratory. 

EFFECT  OF  SALT  ON  GROWTH 

The  rate  of  growth  of  the  White  Wyandotte  chickens  from  June 
19  is  shown  graphically  in  Fig.  2,  the  growth  of  the  White  Leghorns  in 
Fig.  3,  and  the  growth  of  the  Rhode  Island  Red  chickens  in  Fig.  4. 
Among  the  lots  kept  at  the  poultry  farm,  the  growth  of  Lots  1,  2,  3, 
and  5  was  very  similar.  Lot  4,  receiving  8  percent  of  salt  in  its 
ration,  lagged  somewhat  behind  the  other  lots  in  its  rate  of  growth, 
altho  this  is  mainly  due  to  a  retardation  of  growth  in  the  initial  weeks 
of  the  experiment  because  of  the  slow  adjustment  of  the  chickens  to 
the  extremely  salty  ration.  When  the  feed  intake  approximated  that 
of  the  other  groups,  the  rate  of  growth  was  about  the  same  as  that 
of  the  chickens  getting  smaller  percentages  of  salt. 

There  was  some  mortality  among  the  lots  kept  at  the  poultry 
farm,  but  the  cause  of  death  seemed  to  be  unrelated  to  the  method  of 
feeding.  In  Lots  1,  2,  and  3  there  were  no  deaths,  in  Lot  4  one  White 
Wyandotte  chicken  died  one  week  after  experimental  feeding  started, 
and  in  Lot  5  two  White  Leghorn  chickens  died  11  and  32  days,  re- 
spectively, after  experimental  feeding  started.  No  abnormal  symp- 
toms referable  to  the  salt  intake  were  observed  in  any  of  the  groups. 
Group  photographs  of  Lots  1  and  4  getting,  respectively,  1  and  8  per- 
cent of  salt  in  their  feed,  are  shown  in  Figs.  5  and  6.  No  differences 
in  the  condition  of  the  two  groups  of  birds  can  be  seen  from  a  com- 
parison of  these  photographs.  Fig.  7  shows  two  of  the  individual  birds 
in  Lot  4,  one  a  White  Leghorn  and  the  other  a  White  Wyandotte,1 

'Most  of  the  White  Wyandottes  used  in  this  experiment,  including  the  one 
shown  in  Fig.  4,  had  single  combs. 


1926] 


THE  TOXICITT  OF  SALT  FOR  CHICKENS 


139 


TKe     GrowtK     of    WKite    Wyandotte    Chickens    on 

Rations     Differing    Only    in    Their    Content"    of    So.lt 


Lot  I        I  percent   salt 
Lot  Z      2    "     " 
Lot  i      4    " 
Let  48"" 
Let  5       I     


The    GrowtK    of    Whute    LegNorrx    GKicker\s     or\ 

RatioNs     Differmg     Or\ly    ir\  TKeir     Cor\Ter\t    of  Salt 


Fig.  4 

OrowtK   of    RKode    Islorxd     F\ed    CMckerxs    or\ 
Ratior\s     Differing     Only     ir\    TKeir     Content     of    Salt 


140 


BULLETIN  No.  279 


[July, 


FIG.  5. — LOT  1  AFTER  THIRTEEN  WEEKS  ON  A  RATION  CONTAINING 

1  PERCENT  OF  SALT 

No  difference  could  be  observed  in  the  condition  of  the  birds 
in  Lot  1,  which  received  1  percent  of  salt,  and  Lot  4,  which  re- 
ceived 8  percent  (see  Fig.  6). 


FIG.  6. — LOT  4  AFTER  THIRTEEN  WEEKS  ON  A  RATION  CONTAINING 

8  PERCENT  OF  SALT 

The  chickens  in  this  lot  lagged  behind  those  in  the  other  lots 
in  rate  of  growth,  owing  chiefly  to  retardation  of  growth  in  the 
first  weeks  of  the  experiment  before  they  became  adjusted  to  the 
extremely  salty  ration.  When  their  feed  intake  approximated  that 
of  the  other  groups,  the  rate  of  growth  was  about  the  same  as  for 
the  chickens  receiving  less  salt. 


1926]  THE  TOXICITY  OF  SALT  FOR  CHICKENS  141 

taken  at  the  end  of  the  feeding  test.  The  chickens  in  Lot  4,  particu- 
larly, drank  and  excreted  large  amounts  of  water,  this  fact  accounting 
for  their  untidy  appearance. 

The  relative  growth  observed  among  the  five  lots  of  Rhode  Island 
Red  chickens  kept  at  the  laboratory  was  very  similar  to  that  of  the 
birds  kept  at  the  poultry  farm.  The  growth  in  Lot  4  again  was  some- 
what slower  than  that  in  the  lots  getting  smaller  percentages  of  salt, 
but  after  the  birds  became  accustomed  to  the  highly  salty  ration,  the 
growth  in  Lot  4  was  quite  as  rapid  as  that  in  the  other  lots ;  in  fact  it 


FIG.  7. — INDIVIDUAL  BIRDS  FROM  LOT  4  FED  A  RATION   CONTAINING  8 

PERCENT  OF  SALT 

Even  this  extremely  salty  ration  did  not  prove  to  be  poisonous  to 
chickens  that  were  eight  weeks  old  when  the  experiment  was  started. 
It  was  observed,  however,  that  the  chickens  in  this  lot  drank  and  ex- 
creted large  amounts  of  water. 

was  somewhat  better  than  that  observed  in  Lot  3,  which  received  4 
percent  of  salt. 

The  mortality  in  these  lots  also  seemed  to  bear  no  relation  to 
the  method  of  feeding.  One  chicken  in  Lot  1  died  after  6  weeks  of 
feeding,  and  2  chickens  in  Lot  3  after  7  weeks  of  feeding.  Continued 
growth  in  the  lots  kept  in  the  nutrition  laboratory  was  prevented  by 
the  appearance  of  leg  weakness  among  many  of  the  birds.  Whether 
this  was  due  to  the  small  percentage  of  cod-liver  oil  in  the  rations  or 
to  the  confinement  of  the  birds  in  such  small  pens  cannot  be  deter- 
mined.1 It  was  entirely  unrelated  to  the  salt  content  of  the  diet.  The 
feeding  experiment  in  the  laboratory  was  discontinued  one  week  sooner 

'In  an  attempt  to  determine  whether  the  leg  weakness  observed  was  due  to 
rickets  the  tibias  and  fibulas  from  each  of  7  affected  chickens  and  5  unaffected 
chickens  were  dissected  out  and  analyzed  for  ash  and  calcium.  The  bones  were 
ground,  dried,  and  extracted  with  ether  before  analysis.  The  bones  from  3  of 
the  affected  birds  were  normal  in  appearance  and  had  a  normal  content  of  ash 


142  BULLETIN  No.  279  [July, 

than  that  at  the  poultry  farm,  because  of  the  prevalence  of  leg  weak- 
ness, which  interfered  seriously  with  the  feeding  of  many  of  the  birds. 
The  severity  of  this  symptom  is*  illustrated  by  the  three  chickens 
shown  in  Fig.  8. 

The  average  gains  and  average  feed  records  of  the  White  Wyan- 
dotte  and  White  Leghorn  chickens  fed  at  the  poultry  farm  are  given 


FIG.  8. — BIRDS  RAISED  IN  INDIVIDUAL  FEEDING  PENS  IN  THE  NUTRITION 

LABORATORY 

Leg  weakness  developed  in  many  of  the  birds  in  the  laboratory  lots  irre- 
spective of  the  amount  of  salt  in  the  rations..  This  condition  may  have  been 
brought  on  by  the  small  percentage  of  cod-liver  oil  in  the  rations,  or  by  the 
confinement  of  the  birds  in  such  small  pens. 

c 

in  Tables  2  and  3.  The  average  daily  gains  of  Lots  1  and  2  receiving 
1  and  2  percent  of  salt  in  the  feed,  respectively,  were  not  significantly 
different  for  either  breed.  In  Lot  3  the  average  daily  gain  of  the  White 
Leghorns  was  slightly  higher  than  the  gains  for  the  same  breed  in  Lots 
1  and  2.  The  White  Wyandottes  in  Lot  3,  however,  gained  on  the 
average  rather  distinctly  less  per  day  than  the  birds  of  the  same  breed 
in  Lots  1  and  2.  In  view  of  the  great  variability  among  the  individual 
gains  of  Lots  1  and  2,  it  is  probable  that  the  lower  average  gain  in 
Lot  3  bears  no  relation  to  the  larger  intake  of  salt.  The  average  daily 
gain  of  Lot  4,  both  with  the  White  Wyandottes  and  White  Leghorns, 
was  slightly  less  than  the  average  gains  of  the  other  groups,  probably 
due  to  the  longer  time  required  by  the  chickens  in  this  lot  to  become 
accustomed  to  their  ration.  Lot  5,  receiving  the  same  ration  as  Lot  1, 
gained  on  the  average  at  a  distinctly  better  rate,  this  being  true  of  both 
the  White  Wyandotte  and  White  Leghorn  chickens  that  survived  thru- 
out  the  feeding  experiment. 

and  calcium.  The  bones  from  2  of  the  affected  birds  were  bent,  but  otherwise 
normal  in  appearance,  and  showed  a  content  of  ash  and  calcium  somewhat  below 
that  of  most  of  the  bones  from  the  unaffected  birds..  The  bones  from  2  of  the 
affected  birds  were  bent,  soft  at  the  ends,  and  possessed  a  distinctly  subnormal 
percentage  of  ash  and  calcium  and  a  subnormal  percentage  of  calcium  in  the  ash. 
The  bones  from  the  unaffected  birds  were  perfectly  normal  in  appearance  and 
contained  an  average  of  58.95  percent  ash  and  22.35  percent  calcium  on  the  fat- 
and  moisture-free  basis,  and  an  average  of  37.91  percent  calcium  in  the  ash. 


THE  TOXICITY  OF  SALT  FOR  CHICKENS 


143 


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144 


BULLETIN  No.  279 


[July, 


The  average  daily  consumption  of  feed  in  the  lots  kept  at  the 
poultry  farm  was  practically  the  same  for  Lots  1,  2,  3,  and  5,  and 
slightly  less  for  Lot  4.  The  average  amounts  of  feed  required  per 
gram  of  gain  were  6.67  grams  for  Lot  1,  6.72  grams  for  Lot  2,  6.80 
grams  for  Lot  3,  7.01  grams  for  Lot  4,  and  6.08  grams  for  Lot  5.  These 
figures  are  closely  related,  of  course,  to  the  average  daily  gains  of  the 
lots — the  greater  the  average  daily  gain,  the  smaller  the  average 
amount  of  feed  required  per  gram  of  gain. 

The  feed  and  weight  records  for  the  Rhode  Island  Red  chickens 
were  obtained  for  each  individual  bird.  These  records  with  the  group 


TABLE  3. — FEED  RECORDS  FOR  THE  WHITE  WYANDOTTE  AND  WHITE  LEGHORN  LOTS 
Each  lot  contained  5  birds  of  each  breed. 


Lot  1 

Lot  2 

Lot  3 

Lot  4 

Lot5 

Total  feed  

grams 
71  552 

grams 
69  328 

grams 
69  765 

grams 
57  445 

grams 
61  314 

Average  daily  feed. 
Average  daily  gain  . 
Feed  per  gram  gain 

85.18 
12.76 
6.67 

82.52 
12.27 
6.72 

83.05 
12.21 
6.80 

75.29 
10.74 
7.01 

85.75 
14.10 
6.08 

averages  are  given  in  Table  4.  The  average  daily  gains  of  the  five 
lots  were,  respectively,  11.64,  12.72,  9.60,  9.87,  and  11.74  grams.  The 
average  daily  feed  intakes  for  the  five  lots  were  79.6.  81.8,  69.8,  76.2, 
and  76.0  grams.  The  average  economy  of  gains  as  expressed  in  the 
amount  of  feed  required  per  gram  of  gain  was  approximately  the 
same  for  Lots  1,  2,  and  5,  namely,  6.85,  6.50,  and  6.66  grams,  respect- 
ively. The  average  economy  of  gains  in  Lots  3  and  4  was  distinctly 
less,  namely,  7.99  and  7.80  grams  of  feed  per  gram  of  gain,  tho  some 
of  the  individuals  in  these  lots  were  as  economical  in  the  feed  cost  of 
gains  as  individuals  in  the  other  lots. 

It  may  be  concluded  from  the  results  of  these  feeding  experiments 
that  the  rate  and  economy  of  gains  in  growing  chickens  is  distinctly 
retarded  by  8  percent  of  salt  in  the  diet,  tho  this  effect  is  largely 
due  to  a  slow  adjustment  of  the  appetite  of  the  chickens  to  such  a 
salty  ration.  It  cannot  definitely  be  concluded  whether  4  percent  of 
salt  in  the  diet  retards  the  growth  of  chickens.  Some  evidence  favor- 
ing the  belief  that  growth  was  retarded  was  obtained  with  White 
Wyandottes  and  Rhode  Island  Red  chickens,  tho  some  of  the  individ- 
ual gains  obtained  on  the  4-percent  salt  ration  were  as  high  as  or 
higher  than  the  gains  secured  on  the  ration  containing  only  1  percent 
of  salt.  The  Rhode  Island  Red  chickens  receiving  4  percent  of  salt 
showed  such  great  variation  among  the  individual  birds  that  the  aver- 
ages cannot  be  considered  representative  of  the  group. 


1926~\ 


THE  TOXICITY  OF  SALT  FOR  CHICKENS 


145 


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BULLETIN  No.  279 


[July, 


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1926] 


THE  TOXICITY  OF  SALT  FOR  CHICKENS 


147 


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148 


BULLETIN  No.  279 


{.July, 


Information  concerning  the  daily  salt  intake  per  bird  and  per  kilo- 
gram of  body  weight  is  contained  in  Table  5  for  the  White  Wyandotte 
and  White  Leghorn  chickens,  and  in  Table  6  for  the  Rhode  Island  Red 
chickens,  the  individual  data  being  given  in  the  latter  case.  The  aver- 
age daily  intake  of  salt  for  all  groups  ranges  from  0.72  gram  to  6.32 
grams  per  kilogram  of  body  weight.  The  average  daily  intake  of  salt 

TABLE  5. — AVERAGE  SALT  INTAKE  PER  DAY  AND  PER  KILOGRAM  OF  BODY  WEIGHT 
FOR  THE  WHITE  WYANDOTTE  AND  WHITE  LEGHORN  CHICKENS 
Each  lot  contained  5  birds  of  each  breed. 


Lot  1 

Lot  2 

Lot3 

Lot  4 

Lot  5 

Average  weight  

grams 
1  044 

grams 
1  064 

grams 
1  045 

grams 
955 

grams 
1  131 

Average  daily  feed  

85.18 

82  52 

83.05 

75  29 

85.75 

Average  daily  salt  intake  . 
Salt  intake  per  kilogram 
of  body  weight  per  day  . 

0.852 
0.816 

1.650 
1.551 

3.322 
3.179 

6.023 
6.306 

0.857 
0.758 

per  bird  for  the  lots  getting  8  percent  in  their  ration  was  6.32  grams  for 
the  Rhode  Island  Red  chickens  and  6.31  grams  for  the  White  Wyan- 
dottes  and  White  Leghorns.  The  largest  intake  of  salt  per  kilogram  of 
body  weight  per  day  among  the  individual  Rhode  Island  Red  birds  of 
Lot  4  was  6.87  grams  for  bird  No.  1. 

The  figures  just  considered  refer  to  the  average  daily  intake  of 
salt  for  the  entire  period  of  feeding.  For  the  individual  weeks  of  the 
experiment  the  intake  of  salt  was  in  general  higher  in  the  early 
weeks.  For  example,  in  Lot  4  at  the  poultry  farm,  consisting  of  the 
White  Wyandotte  and  White  Leghorn  chickens,  the  average  intake  of 
salt  per  kilogram  of  body  weight  per  day  for  the  first  4  weeks  of  the 
experiment  was,  in  order,  5.66,  8.37,  8.75,  and  6.85  grams. 

The  daily  intake  of  salt  per  kilogram  of  body  weight  for  the  indi- 
vidual Rhode  Island  Red  chickens  in  Lot  4  for  all  weeks  of  the  experi- 
ment will  be  found  in  Table  7.  It  is  evident  that  some  of  the  individ- 
ual birds  in  this  group  tolerated  8  to  9  grams  of  salt  per  kilogram  of 
body  weight  per  day  without  developing  any  pathological  symptoms 
or  showing  a  markedly  diminished  rate  of  growth. 

MINIMUM  LETHAL  DOSE  OF  SALT 

At  the  conclusion  of  the  feeding  experiment  the  birds  were  given 
varying  doses  of  salt,  either  in  the  solid  form  in  capsules,  or  in  a  20- 
percent  solution,  in  order  to  determine  the  maximum  amount  of  salt 
that  could  be  tolerated  both  in  repeated  doses  and  in  single  doses.  In 
the  first  tests  undertaken  in  this  connection,  the  birds  were  given  two 
doses  a  day  at  approximately  8:30  a.  m.  and  4:00  p.  m.  In  these  tests 
the  doses  were  not  adjusted  to  the  size  of  the  bird,  but  in  the  last  test 
the  doses  were  graduated  according  to  the  body  weight. 


1926'}  THE  TOXICITY  OF  SALT  FOR  CHICKENS  149 

The  first  test,  which  was  made  upon  Rhode  Island  Red  chickens 
from  the  laboratory  lots,  was  concerned  with  the  determination  of  the 
maximum  dosage  of  salt  that  could  be  tolerated  by  the  birds  when 
given  repeatedly  at  the  rate  of  two  doses  a  day.  In  the  first  day  of 
the  test  two  doses  of  2,  4,  6,  8,  and  10  grams  were  given  groups  of  3 
or  more  birds  taken  from  Lots  1  to  5.  The  salt  was  given  by  pipette 
in  a  20-percent  solution.  During  the  test  the  birds  had  no  access  to 
feed,  but  water  was  kept  before  them  continually  except  when  the 
water  containers  became  exhausted  at  night.  All  birds  getting  doses 
of  6,  8,  and  10  grams  were  dead  either  on  the  afternoon  of  the  first 
day  or  by  morning  of  the  second  day.  None  of  the  birds  getting  2- 
and  4-gram  doses  died  during  the  first  day.  The  birds  surviving  on 
the  morning  of  the  second  day  were  therefore  divided  into  two  lots  and 
given,  respectively,  4-  and  6-gram  doses.  Of  those  getting  6-gram 
doses,  5  survived  two  doses  only,  and  2  survived  four.  Of  the  birds 
getting  4-gram  doses,  2  survived  four  doses  only,  1  survived  six  doses, 
and  the  other  bird,  which  was  the  lightest  in  the  lot,  tolerated  two 
4-gram  doses  daily  for  about  a  month  with  no  apparent  detriment. 
The  results  of  the  test  are  summarized  in  Table  8.  The  body  weights 
given  in  this  table  were  the  final  weights  of  the  birds  in  the  feeding 
experiment,  which  terminated  exactly  one  week  before  this  test  was 
started. 

The  symptoms  of  the  birds  that  died  were  very  similar  to  those 
that  have  been  reported  in  the  literature.  Intense  thirst  accompanied 
the  treatment  in  all  cases,  and  death  was  preceded  by  a  period  of  ap- 
parent stupor  in  which  the  bird  stood  or  squatted  with  closed  eyes  and 
hanging  head.  No  pronounced  convulsions  were  noted  preceding  death. 

Thru  the  courtesy  of  the  Laboratory  of  Animal  Pathology  and 
Hygiene,  9  of  the  birds  that  succumbed  in  this  test  were  given  post- 
mortem examination  by  Dr.  E.  A.  Tunnicliff.  The  mucous  membrane 
of  the  digestive  tube  was  in  all  cases  found  to  be  irritated,  as  evidenced 
by  hyperemia,  petechia,  'or  ecchymosis  of  the  blood  vessels.  Conges- 
tion of  the  liver  was  a  constant  finding. 

It  is  evident  from  this  test  that  8  grams  of  salt  per  day  could  not 
be  tolerated  continuously  by  a  majority  of  chickens.  Doses  larger 
than  8  grams  per  day  were  quickly  fatal. 

In  continuing  the  experiments  in  the  individual  dosing  of  birds 
with  salt,  the  question  arose  as  to  whether  the  consumption  of  feed 
had  anything  to  do  with  the  survival  period  of  the  birds.  The  second 
test  was  therefore  concerned  with  determining  whether  a  difference  in 
susceptibility  to  salt  poisoning  exists  between  birds  in  a  fasting  and  a 
fed  condition.  Three  groups  of  6  birds  each  taken  from  Lots  1  to  5 
at  the  poultry  farm  were  given,  respectively,  twice  daily,  4-,  5-,  and 
6-gram  doses  of  salt.  In  each  of  the  three  groups  3  of  the  birds  were 


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1926] 


THE  TOXICITY  OF  SALT  FOR  CHICKENS 


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THE  TOXICITY  OF  SALT  FOR  CHICKENS 


153 


fasted  during  the  test  while  the  3  remaining  birds  were  given  access  to 
feed.  The  results  of  this  test  are  summarized  in  Table  9. 

The  results  do  not  show  any  marked  differences  in  the  survival 
period,  whether  the  birds  were  fasting  or  had  access  to  feed.  A  slight 
difference  favoring  the  fasting  birds  may  be  noted,  but  it  is  question- 
able whether  the  difference  is  significant  in  view  of  the  different  be- 
havior among  birds  given  the  same  treatment.  All  doses  proved  to 
be  rather  quickly  fatal,  except  in  the  case  of  one  bird  receiving  8 
grams  of  salt  daily,  which  survived  for  10  days.  The  salt  in  this  test 
was  fed  in  the  solid  form  and  was  administered  in  capsules. 

A  third  test,  the  results  of  which  are  summarized  in  Table  10, 
was  concerned  with  the  toxicity  of  3-,  4-,  and  5-gram  doses  of  salt 
given  twice  daily.  While  the  results  indicate  an  increased  mortality 
with  increasing  dosage,  it  is  evident  that  even  the  smallest  dose  could 
not  be  tolerated  by  these  birds  for  any  great  length  of  time,  altho  the 
birds  in  Lot  4  consumed  an  average  of  over  6  grams  of  salt  daily 
thruout  the  feeding  experiment. 


TABLE  8. — MINIMUM  LETHAL  REPEATED  DOSE  OF  SALT  FOR  RHODE  ISLAND 

RED  CHICKENS 
(Doses  given  twice  daily,  approximately  8:30  a.  m.  and  4:00  p.  m.) 


Bird  No. 

Lot 

Body 
weight1 

Size 
of 
dose 

Number  of 
doses  taken 
before  death 

2.. 

5 

grams 
1  380 

grams 
4 

4 

1  

5 

1  590 

42 

4 

3  

4 

1  590 

4 

6 

2  

4 

1  320 

4 

indefinite4 

4  

1 

1  500 

6 

2 

3  

2 

1  450 

6 

2 

1  

1 

1  360 

62 

2 

1  

2 

1  850 

6 

2 

2  

2 

1  560 

63 

2 

3  

3 

880 

63 

4 

1  

4 

1  190 

62 

4 

5  

1 

1  430 

8 

2 

4  

2 

1  300 

8 

2 

4  

4 

1  400 

8 

2 

4  

5 

1  300 

8 

2 

5.... 

2 

1  640 

10 

2 

5  

4 

1  190 

10 

2 

5  

5 

1  745 

10 

2 

'These  weights  were  taken  7  days  before  the  first  dosage  of  salt. 
2Received  2  dose  i  of  2  grams  of  salt  the  day  before. 
'Received  2  doses  of  4  grams  of  salt  the  day  before. 

4This  chicken  was  given  4  grams  of  salt  twice  daily,  for  almost  a  month,  at  the 
end  of  which  time  it  was  in  good  condition. 


154 


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THE  TOXICITY  OF  SALT  FOR  CHICKENS 


155 


In  the  tests  so  far  reported,  no  attention  was  paid  to  the  body 
weights  of  the  birds,  tho  a  study  of  the  survival  periods  does  not  indi- 
cate that  the  heavier  birds  were  markedly  more  resistant  to  salt  than 
lighter  birds  given  the  same  treatment.  In  the  next  two  tests,  how- 
ever, the  dosage  was  given  in  proportion  to  the  live  weight  of  the 
birds.  In  the  first  of  these  tests,  three  groups  of  4  birds  each  were 
given,  respectively,  2,  4,  and  6  grams  of  salt  per  kilogram  of  body 
weight,  the  salt  being  administered  in  a  20-percent  solution.  Only  one 
dose  was  given  in  this  case,  the  attempt  being  to  find  the  minimum 
lethal  single  dose  of  salt.  All  of  the  birds  getting  the  6-gram  dose  per 


TABLE  10. — MINIMUM  LETHAL  REPEATED  DOSE  OF  SALT  FOR  WHITE  WYANDOTTE 

AND  WHITE  LEGHORN  CHICKENS 
(Doses  given  twice  daily,  approximately  8:30  a.  m.  and  4:00  p.  m.) 


Breed 

Lot 

Bird 
No. 

Body 
weight1 

Size 
of 
dose 

Number  of 
doses  taken 
before  death 

Leghorn  

2 

2 

grams 
1  470 

grams 
3 

3 

Leghorn  

4 

3 

1  330 

3 

3 

Wyandotte  

4 

1 

1  300 

3 

11 

Leghorn        .   . 

3 

2 

1  640 

3 

12 

Wyandotte  

4 

5 

1  990 

3 

12 

Wyandotte  

2 

5 

2  120 

3 

12 

Leghorn  

3 

5 

1  470 

4 

2 

Wyandotte  

4 

3 

1  700 

4 

2 

Leghorn  

4 

2 

1  230 

4 

2 

Leghorn  

2 

3 

1  600 

4 

3 

Wyandotte  

3 

1 

1  610 

4 

8 

Leghorn  

4 

5 

1  400 

4 

10 

Wyandotte  

2 

1 

1  670 

4 

10 

Leghorn  

2 

5 

1  220 

5 

2 

Wyandotte  .... 

3 

3 

1  670 

5 

2 

Leghorn  

4 

2 

1  230 

5 

2 

Wyandotte  

2 

4 

2  120 

5 

3 

Leghorn  

3 

3 

1  690 

5 

3 

Wyandotte  

3 

4 

1  780 

5 

11 

'These  were  the  final  weights  of  the  birds  in  the  feeding  experiment  which  ended 
7  days  before  the  test  reported  upon  in  this  table. 

kilogram  of  body  weight  and  two  of  those  getting  the  4-gram  dose 
were  dead  within  24  hours.  All  other  birds  survived  the  treatment. 
The  test  indicated  that  the  minimum  single  lethal  dose  was  close  to 
4  grams  per  kilogram  of  body  weight. 

In  an  attempt  to  determine  the  minimum  lethal  dosage  more  defi- 
nitely, 6  birds  from  the  White  Wyandotte  and  White  Leghorn  groups 
were  given,  first,  a  single  dose  of  3  grams  of  salt  per  kilogram  of  body 
weight;  no  deaths  occurred  in  the  following  72  hours.  At  the  end  of 
this  time  they  Vere  given  a  second  dose  of  4  grams  of  salt  per  kilo- 


156  BULLETIN  No.  279 

gram  of  body  weight,  and  at  the  end  of  72  hours  all  birds  were  still 
alive.  A  third  dose  of  5  grams  per  kilogram  of  body  weight  was  then 
administered,  and  within  the  following  24  hours  5  of  the  6  birds  had 
died  with  symptoms  typical  of  salt  poisoning.  The  remaining  bird  was 
unaffected.  This  test  indicates  rather  clearly  that  4  to  5  grams  of  salt 
per  kilogram  of  body  weight  is  close  to  the  minimum  lethal  single  dose 
of  salt  when  administered  in  solution.  There  is  no  reason  to  suppose 
that  these  results  would  have  been  different  if  salt  in  solid  form  had 
been  given,  provided  free  access  to  water  had  been  permitted,  as  was 
done  in  all  the  tests  here  reported.  However,  the  preceding  test  indi- 
cates that  4  grams  of  salt  per  kilogram  of  body  weight  in  a  single  dose 
may  be  fatal  to  some  birds. 

CONCLUSIONS 

Chickens  may  be  raised  from  9  to  21  weeks  of  age  on  rations  con- 
taining as  high  as  8  percent  of  salt  with  no  apparent  detrimental  ef- 
iects  on  their  condition.  Furthermore,  after  the  birds  have  become 
accustomed  to  such  salty  rations,  they  will  consume  them  in  such 
amounts  as  to  promote  a  rate  of  growth  approximating  that  of  birds 
receiving  much  smaller  percentages  of  salt  in  their  feed. 

A  daily  intake  of  salt  in  the  feed  of  6  to  8  grams  per  bird  appears 
to  exert  no  harmful  effect  in  birds  of  9  weeks  or  more  in  age. 

For  birds  weighing  from  2  to  4  pounds  each,  12  to  16  grams  of 
sajt  daily  administered  directly  in  the  crop  in  two  equal  doses  is 
quickly  fatal.  Eight  grams  of  salt  daily,  given  in  two  doses,  can  ordi- 
narily be  tolerated  for  as  long  as  5  days,  and  occasionally  indefinitely. 
However,  even  on  this  dosage  death  within  24  hours  may  occur  in  some 
cases.  Six  grams  per  day  given  in  two  portions  is  generally  tolerated 
for  5  to  6  days,  tho  in  a  small  proportion  of  cases  death  results  much 
sooner. 

Salt  administered  in  solution  twice  daily  cannot  be  tolerated  so 
well  as  equal  amounts  of  salt  ingested  with  the  feed.  However,  the 
consumption  of  feed  after  the  administration  of  toxic  doses  of  salt  by 
injection  into  the  crop,  does  not  alleviate  the  symptoms  produced  nor 
prolong  the  life  of  the  bird  to  an  appreciable  extent. 

The  minimum  lethal  single  dose  of  salt  for  birds  weighing  from 
3  to  5  pounds  is  close  to  4  grams  per  kilogram  of  body  weight.  Most 
of  the  birds  so  treated  survive,  tho  a  few  may  succumb  within  24 
hours.  Birds  given  3  grams  of  salt  per  kilogram  of  body  weight  sur- 
vive the  treatment. 


UNIVERSITY  OF  ILLINOIS-URBANA 


